Is there a way to force employee or user record usernames to upper or lower case?

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Our employee records' usernames are all uppercase so I tried to update the user records so they would all be uppercase, however, when I save it changes them to lowercase. Very, very confusing to our managers and a lot of extra work for me because they forget logins are case-sensitive and forget that their employee account is upper-case and their user account is lower-case.

Any way to control this by perform settings?

Thanks!

Bill